Atomic layer deposited titanium dioxide (ALD-TiO2) has emerged as an effective protection layer for highly efficient semiconductor anodes which are normally unstable under the potential and pH conditions used to oxidize water in a photoelectrochemical cell. The failure modes of silicon anodes coated with an Ir/IrO x oxygen evolution catalyst layer are investigated, and poor catalyst/substrate adhesion is found to be a key factor in failed anodes. Quantitative measurements of interfacial adhesion energy show that the addition of TiO2 significantly improves reliability of anodes, yielding an adhesion energy of 6.02 ± 0.5 J/m2, more than double the adhesion energy measured in the absence of an ALD-TiO2 protection layer. These results indicate the importance of catalyst adhesion to an interposed protection layer in promoting operational stability of high efficiency semiconducting anodes during solar-driven water splitting.
Keywords: adhesion; atomic layer deposition; failure mode; isotope; water oxidation.